Light sensitive switching unit



2 Sheets-Sheet 1 INVENTORS KHrsunorD MmmD/s lim/51w. lrohueo ATTORNEYS Dec. 15, 1970 KATSUMOTO NAKADE E LIGHT SENSITIVE SWITCHING UNI'T Filed Aug. 29, 1968 FIGZ/ Dec. 15, 1970 KATSUMOTO NAKADE ETAL 3,5

LIGHT SENSITIVE SWITCHING UNIT Filed Aug. 29, 1968 2 Sheets-Sheet 2 INVENTORS lffiTJUJIUTO I a/090E J/l/ERLL Irmrwso ATTORNEYS Patented Dec. 15, 1970 3,548,262 LIGHT SENSITIVE SWITCHING UNIT Katsumoto Nakade, Toyonaka-shi, and Shigeru Kokubo,

Osaka, Japan, assignors to Matsushita Electric Industrial Co., Ltd., Osaka, Japan, a corporation of Japan Filed Aug. 29, 1968, Ser. No. 756,106 Int. Cl. H01h 37/72, 47/24; H011 33/54 US. Cl. 317--124 4 Claims ABSTRACT OF THE DISCLOSURE An automatic switching device which is so designed that when automatic switch means is not mounted, a load circuit, such as an illumination lamp, is closed automatically, whereas when the automatic switch means is plugged in a socket and turned into a locked position, movable contacts which are usually closed are opened and a switching circuit is connected across said movable contacts for automatic switching operation.

The present invention relates to an automatic switching device and more particularly to an automatic switching device for an illumination lamp, which is so designed that when switch means is not in service, a load circuit is closed but said switch means may be readily connected to the circuit by plugging it in a socket and turning the same into a locked position.

As detachable switch means, a three-terminal automatic switch has been known which is connected to a circuit merely by plugging it in a socket. Switches of this type are liable to drop when plugged in an upward direction. In order to avoid the danger of dropping, the socalled locking-type automatic switch has been proposed but the switch of such a structure has the drawbacks that a load circuit is not closed automatically upon removal of the switch, that it is complicate in structure rendering itself unsuitable for mass production and expensive.

It is therefore an object of the present invention to eliminate the foregoing drawbacks of the prior art switches.

It is another object of the present invention to provide an automatic switching device which comprises a combination of switch means and a socket adapted to close a load circuit in normal condition, that is, when the switch means is not plugged therein.

It is still another object of the invention to provide switch means which is small in size and suitable for mass production, and can be locked by turning.

An embodiment of the present invention includes detachable switch means having a common electrode located centrally thereof and an electrode for a power source and an electrode for a load arranged symmetrically with respect to said common electrode, and a socket adapted to close a load circuit normally, the arrangement being such that when the switch means is plugged in the socket, movable contacts in said socket connecting one terminal of a load with one terminal of the power source are opened and a switching circuit, including a bimetaloperated contact, is connected across said movable contacts, while a control circuit, including a photoelectric cell for controlling the switching operation of the switching circuit, is connected across both terminals of the power source.

The present invention will be described in detail hereunder with reference to the accompanying drawings, in which:

FIG. 1 is a front view, in cross-section, of the automatic switching means according to the present invention;

FIG. 2 is a side view, in cross-section, of the switch means shown in FIG. 1;

FIG. 3 is a back view, in cross-section, of the switch means shown in FIGS. 1 and 2;

FIG. 4 is a bottom view of the switch means shown in FIGS. 1, 2 and 3;

FIG. 5 is a plan view of the socket according to the present invention;

FIG. 6 is a bottom view of the socket shown in FIG. 5;

FIG. 7 is a bottom view of the socket shown in FIGS. 5 and 6 with a base plate 27 removed;

FIG. 8 is a bottom view of the socket shown in FIGS. 5, 6 and 7 with the automatic switch means of FIGS. 1 to 4 plugged therein;

FIG. 9 is a side view showing the manner in which the automatic switch means of FIGS. 1 to 4 is plugged in the socket of FIGS. 5 to 7; and

FIG. 10 is an illustrative circuit diagram.

Referring to the drawings, particularly to FIGS. 1 to 4, the switch includes a photoelectric cell 1, such as CdS cell, whose resistance value is variable with the quantity of light. One end of the photoelectric cell 1 is connected to one end of a heating resistance 4 through a soft lead wire 2, which heating resistance, as seen in FIGS. 1 and 2, is arranged on a bimetal 3 with the other end thereof secured to a portion of said bimetal. The bimetal 3 carries at one end thereof a contact 5 which performs a switch ing operation in cooperation with a contact 15 upon deformation of said bimetal by the heat generated by the heating resistance 4. The other end of the bimetal 3 is connected to an electrode 6 for power source through a conductor plate 7. The other end of the photoelectric cell 1 is connected to a common electrode 8 through a bracket 9. The contact 15 is provided on a contact spring 11 which is connected to an electrode 10 for load.

The connections among these elements will be readily understood from the circuit diagram of FIG. 10.

The photoelectric cell 1 is supported by the U-shaped bracket 9 by the common electrode 8 located centrally of the entire switch and screw threaded thereinto, and receives a light in the direction of the arrows.

On the other hand, the bimetal 3 is secured by a screw 13 to the conductor plate 7 which is fixed to a base 12 at one end, and electrically connected to the electrode 6 for power source therethrough. The heating resistance 4 has one end connected to the bimetal 3 by a metallic band 14 and the other end electrically connected to the photoelectric cell 1 through the lead wire 2. The contact 5 on the bimetal 3 is held in contact with the contact 15 in the stretched state. By removing the metallic band 14 and the screw 13, the bimetal 3 can be demounted and replaced with a new one or one of different characteristics.

The electrode 6 for power source and the electrode 10 for load are arranged symmetrically with respect to the common electrode 8. Reference numeral 16 designates a stud which in the plugging of the switch into a socket 20 with the electrodes 6 and 10 positioned oppositely to the correct positions, will abut against the front face of said socket and thereby prevent erroneous engagement of the switch with the socket, which would otherwise be possible due to the symmetry of said electrodes.

Reference numeral 17 designates a permanent magnet to attract the bimetal 3, 18 a screw to effect a return movement of the bimetal and 19 a light-permeable plastic case which serves to protect the parts disposed interior thereof.

The overall structural arrangement of the switch is such that the light-receiving element is disposed in the top portion, the operating mechanism in the middle portion, and the electrode 6 for power source, the electrode for load and the common electrode 8 at the lower portion of the switch, so that the switch takes a minimum space, enables the parts to be mounted and demounted in one direction, facilitates ease of assembling and is therefore suitable for mass production, is beautiful in appearance and simple in structure.

The state in which the device of the present invention is used will be explained with reference to the circuit diagram of FIG. 10. The socket comprises movable contact strips 21, 22 in contact with each other and a common contact strip 23. When the automatic switch 50 is not plugged in the socket 20, the contact strips 21, 22 are maintaiend in contact with each other, electrically connecting a power source directly with a load 24, whereas when the automatic switch 50 is plugged in the socket 20 and turned, the power source 25 is connected to the load 24 through the switching circuit (6, 7, 3, 5, 15, 11 and 10). A control circuit comprising the photoelectric cell 1 and the heating resistor 4, etc. causes a switching operation of the switching circuit in response to the quantity of light received by said photoelectric cell, whereby the load 24 is switched on and off. More specifically, as the quantity of light received by the photoelectric cell 1 increases, the resistance of said photoelectric cell decreases, so that more current flows through the heating resistance 4 and consequently the bimetal is heated. If, in this case, the bimetal is subjected to a deformation to such an extent as to cause the contact 5 to be disconnected from the contact 15, the circuit of the load 24, such as an illumination lamp, is opened when a quantity of light more than a predetermined quantity is received by the photoelectric cell. As the resistance of the photoelectric cell 1 decreases with the quantity of light received by the photoelectric cell decreasing, the current passing through the heating resistance 4 also decreases, and thus the contacts 5 and 15 are closed and the circuit of the load 24 is closed accordingly. Thus, it will be understood that in the case that the load 24 is an illumination lamp, the lamp can be automatically switched on only when the surrounding area is dark.

Next, the practical structure of the socket will be described with reference to FIGS. 5 to 7. The aforesaid movable contact strip 21 is connected to the power source and the movable contact strip 22 to the load at one of their ends respectively and the other of their ends are normally closed in contact with each other as shown in FIG. 7 under the biasing forces thereof. These contact strips 21, 22 are housed in a casing 26 and secured in position by respective projections in such a manner that they are allowed to bend only in the directions of the arrows B in FIG. 8 respectively. The open end of the casing 26 is closed by a base plate 27 so as to prevent the contact strips from jumping out of said casing.

The common contact strip 23 is secured to the base plate 27 as by a rivet 28, and is yieldingly pushed upward by the common electrode 8 of the automatic switch 50 and thereby remains in contact with the latter when said automatic switch is plugged in the socket. As the automatic switch 50 is turned after being plugged in the socket, the electrode 6 for power source and the electrode 10 for load urge the respective contact strips 21, 22 to bend in the directions of the arrows B and, when said automatic switch is further turned through a prescribed angle, said electrodes are hooked by curved portions of the respective contact strips, whereby the automatic switch 50 is locked in its position. In this case, since the electrodes 6 and 10 are provided with a stopper flange respectively for engagement with the casing 26, the automatic switch 50 will not be disengaged from the socket even when a force is imposed thereon in the direction C in FIG. 9.

On the other hand, when it is desired to disengage the automatic switch from the socket, this can be attained readily by turning the automatic switch in a reverse direction and pulling the same in the direction C. In order to facilitate rotation of the automatic switch 50, the common electrode 38 is disposed centrally of the switch and the electrodes 6 and 10 symmetrically with respect to said common electrode, it is possible for the user to inadvertently plug the switch in the socket in a wrong position. For the purpose of preventing this, the stud 16 is provided on the automatic switch, while a slot 29 is formed in the socket for receiving said stud 16. The common contact strip 23 is electrically insulated completely from the contact strips 21, 22 by the base plate 27.

As described above, the socket is composed of a small number of parts, i.e., the contact strips 21, 22 which are identical in shape and size, the common contact strip 23, the insulating base plate 27 which simultaneously serves as a bracket for said common contact strip, and the casing 26, and therefore is very simple in structure.

Further, according to the present invention, the automatic switch is detachable freely and therefore can be replaced simply when it has failed or its service life has expired.

Still further, the device of the present invention has the advantage that the electric circuit can be checked with ease, and can be handled in a simple manner, and thus is of great practical value.

What is claimed is:

1. An automatic switching device including a socket for receiving an automatic switch means and having normally closed movable contact strips through which a load may be connected with a power source; said automatic switch means comprising a base provided with three cylindrical electrodes, a switching circuit connected across two electrodes of said cylindrical electrodes and a control circuit connected across the remaining electrode and a common electrode that is one of said two electrodes; said automatic switch means being plugged into said socket by said three electrodes to control switching of the load and being turnable for locking; and being so arranged that when said switch means is plugged in said socket, said movable contact strips are opened and said switching circuit is connected across said contact strips, while said control circuit for controlling said switching circuit is connected across both terminals of the power source.

2. An automatic switching device as defined in claim 1, wherein each of said movable contact strips consists of an elastic conductor movable only in one direction and when said automatic switch means is plugged in said socket and turned, both ends of said switching circuit moves said elastic conductors apart from each other and are connected to said respective elastic conductors.

3. An automatic switching device as defined in claim 2, wherein said common electrode, and the other terminal of the control circuit is composed of a projecting electrode provided centrally of the bottom face of said automatic switch means, said projecting electrode simultaneously serving as a pivot pin during mounting and demounting of said automatic switch means.

4. A combination of automatic switch means and an automatically closing-type socket; said automatic switch means comprising a casing, a light-receiving element disposed in the upper portion of said casing, an operating mechanism disposed in the middle portion of said casing and including a removable bimetal 3 and screws, a cylindrical common electrode 8 disposed centrally of the lower end face of said casing and electrically mechanically connected with said operating mechanism, a cylindrical electrode 6 for power source and a cylindrical electrode 10 for load which are disposed on the lower end face of said casing in symmetrical relation with respect to said common electrode 8, and a stud 16 provided on said lower end face of the casing for determining the position of said automatic switch means for satisfactory engagement of said switch means with said socket; and said socket comprising a casing 26, a contact strip 21 for power source and a contact strip 22 for load which are symmetrical in shape and disposed in said casing 26 with one of their ends thereof normally in contact with each other under their own biasing forces, a base plate 26 closing the open end of said casing and a common contact strip 20 fixed to said base plate 26 at one end thereof, said casing having a slot 29 formed in References Cited UNITED STATES PATENTS 10 ROY LAKE, Primary Examiner C. R. CAMPBELL, Assistant Examiner US. Cl. X.R.

the front surface thereof for engagement with said stud 16. 15 20 51 1; 3 7 117; 315 159 

